In order to maintain production of an existing well it sometimes becomes desirable to clean the tubing bore of mineral and other deposits. These deposits not only tend to reduce product flow through the tube, but also obstruct the passage of other workover tools, which may be employed to enhance production. High-speed rotary jetting tools are in common use on coiled tubing workover rigs for this purpose. In general, these so called “whirl jets” have radially directed jets in combination with tangentially directed jets that make the tool spin at essentially uncontrolled speeds ranging from 500 to 5,000 rpm. Tool rotation is deemed to be necessary in order to clean the entire inside surface of the tube. The down side of this whirling action is that jet impact is not focused on any point but rather, it loses its integrity and is sprayed along a path around the tubing bore. The higher the speed of rotation, the longer the path and the less effective the cleaning action. As a result, whirl jets are generally considered to be bore washing devices rather than bore cleaning devices.
The most effective jetting tool for breaking-up mineral deposits would be non-rotating, but since it is necessary to clean the entire bore of the tube, some rotation is obviously desirable. Whirl jets may have a combination of radial and tangential jets but none in the prior art have achieved a controlled, slow speed of considerably less than 100 rpm, as is necessary for effective bore cleaning.
A first object of the present invention is therefore, to provide a slowly rotating jetting tool for removal of hard mineral deposits in a well bore. A second object is that the tool rotational speed be less than 60 rpm, so as not to unduly diminish jet impingement velocity and impact for deposit removal purposes and a third object is that the rotational speed is stable and not affected by operating conditions. A fourth object of the present inventions is that the jetting tool be centralized in the well tube for stability and more uniform cleaning action. Yet other objects of the present inventions are that the jetting tool be inexpensive to manufacture and easy to maintain.